I shared a poem on my other blog that reminded me of a conversation I had with a friend earlier this year about kids asking what a word or concept means. The ones that seem easy are usually traps.
Or, as he described it, you get excited at first because you think, “oh, this is easy, I can totally explain this.”
And then you end up going down this mental path of realizations like “oh, wait, you don’t know what that is so I can’t use that example” and “how can I explain this using an experience you’ve had” and “if I use this word this way now is it going to mess you up later?” (That last one might be my more recent addition.) You do this until you arrive at the realization that this “easy” thing is actually really difficult to explain without a certain set of prior knowledge and/or shared touchpoints.
I experienced this recently trying to explain the concept of “sooner” to a 4 year old.